The Food of the Smaller Fresh- Water Fishes. 
73 
Four-fifths of the food of the genus consisted of animal matter, 
nearly one-quarter being Mollusca, including Physa, Planorbis, 
and Valvata sincera. Insects make less than half, and nearly 
half of these were of terrestrial origin. Chironomus larvae, usually 
so abundant in the food of insectivorous minnows, occurred here 
in only trivial quantity. Specimens of Philhydrus were eaten by 
three of the fishes. Corixci alternata amounted to five per cent, 
of their food, Agrion larvae and case worms (Leptoceridae) to two 
per cent. Crustaceans were only four per cent, of the whole, 
partly Amphipoda, but chiefly Entomostraca. The vegetable 
food (sixteen per cent.) was chiefly Wolffia, taken by five of the 
specimens from southern lakes. Ten individuals had, however, 
eaten filamentous Algae. 
Summary. 
The only essential difference between these two genera exhib- 
ited by the specimens studied, is the much larger ratios of terres- 
trial insects captured by Zygonectes, this genus eating nearly 
twice as many as the other. This fact is possibly related to the 
surface-swimming habit already mentioned, but is more likely due 
to the smaller bodies of water in which the top minnows occur. 
Concerning the food of the family as a whole, the salient charac- 
ters are the presence of a considerable quantity of vegetable food, 
(about twenty per cent.) the occurrence of fifteen per cent, of Mol- 
lusca, the insignificant quantity of Crustacea eaten (four per cent.), 
and the importance of terrestrial insects as a source of support. 
FAMILY UMBRIDiE. 
Umbra limi, Kirt. Mud Minnow. 
This species, the only one of its family in Illinois, is very abund- 
ant in muddy ponds and ditches, and has been collected by us 
from Lake to Union Counties. 
The intestine is short, less than the body in length; the gill- 
rakers are thick and rather long, about one-half the length of the 
filaments, and the pharyngeal apparatus is wholly insignificant. 
Ten specimens were studied, from six localities, all from South- 
ern Illinois but one, which was taken in Calumet River. Vegeta- 
ble food amounted to forty per cent., chiefly Wolffia, eaten by 
